Elastomeric compounds incorporating partially coated carbon blacks

ABSTRACT

Disclosed are elastomeric compounds including an elastomer, a silica coated carbon black, and optionally including a coupling agent. Elastomeric compounds incorporating an elastomer and an oxidized, partially coated carbon black are also disclosed. Also disclosed are silica coated carbon black/elastomeric formulations using a variety of elastomers useful in a variety of product applications.

This application is a Continuation-in-Part of U.S. patent applicationNos. 08/446,140, filed May 22, 1995 now abandoned, and 08/528,896, filedSep. 15, 1995 now abandoned, and is a National Phase Application ofPCT/US96/07309, filed May 21, 1996.

TECHNICAL FIELD

The present invention relates to novel elastomeric compounds exhibitingimproved hysteresis properties. More particularly, the invention relatesto novel elastomeric compounds incorporating silica coated carbonblacks.

BACKGROUND ART

Carbon blacks are widely used as pigments, fillers and reinforcingagents in the compounding and preparation of rubber and otherelastomeric compounds. Carbon blacks are particularly useful asreinforcing agents in the preparation of elastomeric compounds used inthe manufacture of tires.

Carbon blacks are generally produced in a furnace-type reactor bypyrolyzing a hydrocarbon feedstock with hot combustion gases to producecombustion products containing particulate carbon black. Carbon blackexists in the form of aggregates. The aggregates, in turn are formed ofcarbon black particles. However, carbon black particles do not generallyexist independently of the carbon black aggregate. Carbon blacks aregenerally characterized on the basis of analytical properties,including, but not limited to particle size and specific surface area;aggregate size, shape, and distribution; and chemical and physicalproperties of the surface. The properties of carbon blacks areanalytically determined by tests known to the art. For example, nitrogenadsorption surface area (measured by ASTM test procedure D3037-Method A)and cetyl-trimethyl ammonium bromide adsorption value (CTAB) (measuredby ASTM test procedure D3765 09.01!), are measures of specific surfacearea. Dibutylphthalate absorption of the crushed (CDBP) (measured byASTM test procedure D3493-86) and uncrushed (DBP) carbon black (measuredby ASTM test procedure D2414-93), relates to the aggregate structure.The bound rubber value relates to the surface activity of the carbonblack. The properties of a given carbon black depend upon the conditionsof manufacture and may be modified, e.g., by altering temperature,pressure, feedstock, residence time, quench temperature, throughput, andother parameters.

It is generally desirable in the production of tires to employ carbonblack-containing compounds when constructing the tread and otherportions of the tire. For example, a suitable tread compound will employan elastomer compounded to provide high abrasion resistance and goodhysteresis balance at different temperatures. A tire having highabrasion resistance is desirable because abrasion resistance isproportional to tire life. The physical properties of the carbon blackdirectly influence the abrasion resistance and hysteresis of the treadcompound. Generally, a carbon black with a high surface area and smallparticle size will impart a high abrasion resistance and high hysteresisto the tread compound. Carbon black loading also affects the abrasionresistance of the elastomeric compounds. Abrasion resistance increaseswith increased loading, at least to an optimum point, beyond whichabrasion resistance actually decreases.

The hysteresis of an elastomeric compound relates to the energydissipated under cyclic deformation. In other words, the hysteresis ofan elastomeric composition relates to the difference between the energyapplied to deform the elastomeric composition and the energy released asthe elastomeric composition recovers to its initial undeformed state.Hysteresis is characterized by a loss tangent, tan δ, which is a ratioof the loss modulus to the storage modulus (that is, viscous modulus toelastic modulus). Tires made with a tire tread compound having a lowerhysteresis measured at higher temperatures, such as 40° C. or higher,will have reduced rolling resistance, which in turn, results in reducedfuel consumption by the vehicle using the tire. At the same time, a tiretread with a higher hysteresis value measured at low temperature, suchas 0° C. or lower, will result in a tire with high wet traction and skidresistance which will increase driving safety. Thus, a tire treadcompound demonstrating low hysteresis at high temperatures and highhysteresis at low temperatures can be said to have a good hysteresisbalance.

There are many other applications where it is useful to provide anelastomer exhibiting a good hysteresis balance but where the abrasionresistance is not an important factor. Such applications include but arenot limited to tire components such as undertread, wedge compounds,sidewall, carcass, apex, bead filler and wire skim; engine mounts; andbase compounds used in industrial drive and automotive belts.

Silica is also used as a reinforcing agent (or filler) for elastomers.However, using silica alone as a reinforcing agent for elastomer leadsto poor performance compared to the results obtained with carbon blackalone as the reinforcing agent. It is theorized that strongfiller-filler interaction and poor filler-elastomer interaction accountsfor the poor performance of silica. The silica-elastomer interaction canbe improved by chemically bonding the two with a chemical couplingagent, such as bis (3-triethoxysilylpropyl) tetra-sulfane, commerciallyavailable as Si-69 from Degussa AG, Germany. Coupling agents such asSi-69 create a chemical linkage between the elastomer and the silica,thereby coupling the silica to the elastomer.

When the silica is chemically coupled to the elastomer, certainperformance characteristics of the resulting elastomeric composition areenhanced. When incorporated into vehicle tires, such elastomericcompounds provide improved hysteresis balance. However, elastomercompounds containing silica as the primary reinforcing agent exhibit lowthermal conductivity, high electrical resistivity, high density and poorprocessibility.

When carbon black alone is used as a reinforcing agent in elastomericcompositions, it does not chemically couple to the elastomer but thecarbon black surface provides many sites for interacting with theelastomer. While the use of a coupling agent with carbon black mightprovide some improvement in performance to an elastomeric composition,the improvement is not comparable to that obtained when using a couplingagent with silica.

It is an object of the present invention to provide novel elastomericcompounds exhibiting improved hysteresis balance. It is another objectto provide an elastomeric compound incorporating silica coated carbonblacks. It is yet another object of the present invention to provide anelastomeric compound incorporating silica coated carbon blacks, whereinthe carbon black may be efficiently coupled to the elastomer with acoupling agent. Such a carbon black may be employed for example, in tirecompounds, industrial rubber products and other rubber goods. It is afurther object of the present invention to provide silica coated carbonblack/elastomeric formulations using a variety of elastomers useful in avariety of product applications. Other objects of the present inventionwill become apparent from the following description and claims.

DISCLOSURE OF THE INVENTION

The present invention is directed to an elastomeric compound includingan elastomer and a silica coated carbon black, and optionally includinga coupling agent. The silica coated carbon black imparts to theelastomer improved hysteresis compared to an uncoated carbon black. Theinvention is also directed to silica coated carbon black/elastomericformulations using a variety of elastomers useful in a variety ofproduct applications.

DETAILED DESCRIPTION OF THE INVENTION

Elastomeric compounds having desirable hysteresis and other propertiesmay be obtained by compounding an elastomer with a silica coated carbonblack.

The silica coated carbon blacks may be obtained by coating a siliconoxide compound onto at least a portion of the carbon black aggregate.Any carbon black may be used.

The carbon black may be fully or partially coated with a silicon oxidecompound by a number of different methods. One such method is taught inJapanese (Kokai) patent application No. HEI 5(1993)-178604. To preparethe silica coated carbon black, an organo-silicate such astetraethylorthosilicate, or a silane such as tetraethoxysilane, may bediluted with a solvent such as methanol to produce a silicon compoundsolution having a concentration of between about 1 and 20% by weight ofthe silicon compound. Another solution is made by adding 5-20% of a 28%aqueous ammonia solution to ethanol.

A carbon black is then slowly added to the ammonia solution, whilecontinuously stirring the mixture. Simultaneously, the silicon compoundsolution is added dropwise to the ammonia solution. After up to severalhours of this operation, the silica coated carbon black is extracted,filtered and dried.

A carbon black coated with silica, thus made, is expected to impartadvantages over carbon black, silica, or mixtures thereof in anelastomer. Without being bound by theory, it is believed that such asilica coated carbon black would have more functional groups,specifically silanols, on its surface, allowing for greater interactionwith a coupling agent, thereby improving hysteresis when compounded withan elastomer compared to uncoated carbon black. The silica coated carbonblack is also expected to impart significant advantages over silica inan elastomer. Accordingly, less coupling agent would be required,resulting in reduced compounding costs.

Elastomeric compounds incorporating a silica coated carbon black asdisclosed above may be additionally compounded with one or more couplingagents to further enhance the properties of the elastomeric compound.Coupling agents, as used herein, include, but are not limited to,compounds that are capable of coupling fillers such as carbon black orsilica to an elastomer. Useful coupling agents include, but are notlimited to, silane coupling agents such asbis(3-triethoxysilylpropyl)tetrasulfane (Si-69),3-thiocyanatopropyl-triethoxy silane (Si-264, from Degussa AG),γ-mercaptopropyl-trimethoxy silane (A189, from Union Carbide Corp.,Danbury, Conn.); zirconate coupling agents, such as zirconiumdineoalkanolatodi(3-mercapto) propionato-O (NZ 66A, from KenrichPetrochemicals, Inc., of Bayonne, N.J.); titanate coupling agents; nitrocoupling agents such asN,N'-bis(2-methyl-2-nitropropyl)-1,6-diaminohexane (Sumifine 1162, fromSumitomo Chemical Co., Japan); and mixtures of any of the foregoing. Thecoupling agents may be provided as a mixture with a suitable carrier,for example X50-S, a mixture of Si-69 and N330 carbon black, availablefrom Degussa AG.

The silica coated carbon blacks incorporated in the elastomeric compoundof the present invention may be oxidized and/or combined with a couplingagent. Suitable oxidizing agents include, but are not limited to, nitricacid and similar compounds. Coupling agents include, but are not limitedto, any of the coupling agents set forth above.

The partially coated embodiments of the present invention may furtherhave an organic group attached. One process for attaching an organicgroup to the carbon black involves the reaction of at least onediazonium salt with a carbon black in the absence of an externallyapplied current sufficient to reduce the diazonium salt. That is, thereaction between the diazonium salt and the carbon black proceedswithout an external source of electrons sufficient to reduce thediazonium salt. Mixtures of different diazonium salts may be used. Thisprocess can be carried out under a variety of reaction conditions and inany type of reaction medium, including both protic and aprotic solventsystems or slurries.

In another process, at least one diazonium salt reacts with a carbonblack in a protic reaction medium. Mixtures of different diazonium saltsmay be used. This process can also be carried out under a variety ofreaction conditions.

Preferably, in both processes, the diazonium salt is formed in situ. Ifdesired, in either process, the carbon black product can be isolated anddried by means known in the art. Furthermore, the resultant carbon blackproduct can be treated to remove impurities by known techniques. Thevarious preferred embodiments of these processes are discussed below.

The processes can be carried out under a wide variety of conditions andin general are not limited by any particular condition. The reactionconditions must be such that the particular diazonium salt issufficiently stable to allow it to react with the carbon black. Thus,the processes can be carried out under reaction conditions where thediazonium salt is short lived. The reaction between the diazonium saltand the carbon black occurs, for example, over a wide range of pH andtemperature. The processes can be carried out at acidic, neutral, andbasic pH. Preferably, the pH ranges from about 1 to 9. The reactiontemperature may preferably range from 0° C. to 100° C.

Diazonium salts, as known in the art, may be formed for example by thereaction of primary amines with aqueous solutions of nitrous acid. Ageneral discussion of diazonium salts and methods for their preparationis found in Morrison and Boyd, Organic Chemistry, 5th Ed., pp. 973-983,(Allyn and Bacon, Inc. 1987) and March, Advanced Organic Chemistry:Reactions, Mechanisms, and Structures, 4th Ed., (Wiley, 1992). Accordingto this invention, a diazonium salt is an organic compound having one ormore diazonium groups.

The diazonium salt may be prepared prior to reaction with the silicacoated carbon black or, more preferably, generated in situ usingtechniques known in the art. In situ generation also allows the use ofunstable diazonium salts such as alkyl diazonium salts and avoidsunnecessary handling or manipulation of the diazonium salt. Inparticularly preferred processes, both the nitrous acid and thediazonium salt are generated in situ.

A diazonium salt, as is known in the art, may be generated by reacting aprimary amine, a nitrite and an acid. The nitrite may be any metalnitrite, preferably lithium nitrite, sodium nitrite, potassium nitrite,or zinc nitrite, or any organic nitrite such as for exampleisoamylnitrite or ethyinitrite. The acid may be any acid, inorganic ororganic, which is effective in the generation of the diazonium salt.Preferred acids include nitric acid, HNO₃, hydrochloric acid, HCl, andsulfuric acid, H₂ SO₄.

The diazonium salt may also be generated by reacting the primary aminewith an aqueous solution of nitrogen dioxide. The aqueous solution ofnitrogen dioxide, NO₂ /H₂ O, provides the nitrous acid needed togenerate the diazonium salt.

Generating the diazonium salt in the presence of excess HCl may be lesspreferred than other alternatives because HCl is corrosive to stainlesssteel. Generation of the diazonium salt with NO₂ /H₂ O has theadditional advantage of being less corrosive to stainless steel or othermetals commonly used for reaction vessels. Generation using H₂ SO₄/NaNO₂ or HNO₃ /NaNO₂ are also relatively non-corrosive.

In general, generating a diazonium salt from a primary amine, a nitrite,and an acid requires two equivalents of acid based on the amount ofamine used. In an in situ process, the diazonium salt can be generatedusing one equivalent of the acid. When the primary amine contains astrong acid group, adding a separate acid may not be necessary. The acidgroup or groups of the primary amine can supply one or both of theneeded equivalents of acid. When the primary amine contains a strongacid group, preferably either no additional acid or up to one equivalentof additional acid is added to a process of the invention to generatethe diazonium salt in situ. A slight excess of additional acid may beused. One example of such a primary amine is para-aminobenzenesulfonicacid (sulfanilic acid).

In general, diazonium salts are thermally unstable. They are typicallyprepared in solution at low temperatures, such as 0-5° C., and usedwithout isolation of the salt. Heating solutions of some diazonium saltsmay liberate nitrogen and form either the corresponding alcohols inacidic media or the organic free radicals in basic media.

However, the diazonium salt need only be sufficiently stable to allowreaction with the carbon black. Thus, the processes can be carried outwith some diazonium salts otherwise considered to be unstable andsubject to decomposition. Some decomposition processes may compete withthe reaction between the carbon black and the diazonium salt and mayreduce the total number of organic groups attached to the carbon black.Further, the reaction may be carried out at elevated temperatures wheremany diazonium salts may be susceptible to decomposition. Elevatedtemperatures may also advantageously increase the solubility of thediazonium salt in the reaction medium and improve its handling duringthe process. However, elevated temperatures may result in some loss ofthe diazonium salt due to other decomposition processes.

Reagents can be added to form the diazonium salt in situ, to asuspension of carbon black in the reaction medium, for example, water.Thus, a carbon black suspension to be used may already contain one ormore reagents to generate the diazonium salt and the processaccomplished by adding the remaining reagents.

Reactions to form a diazonium salt are compatible with a large varietyof functional groups commonly found on organic compounds. Thus, only theavailability of a diazonium salt for reaction with a carbon black limitsthe processes of the invention.

The processes can be carried out in any reaction medium which allows thereaction between the diazonium salt and the carbon black to proceed.Preferably, the reaction medium is a solvent-based system. The solventmay be a protic solvent, an aprotic solvent, or a mixture of solvents.Protic solvents are solvents, like water or methanol, containing ahydrogen attached to an oxygen or nitrogen and thus are sufficientlyacidic to form hydrogen bonds. Aprotic solvents are solvents which donot contain an acidic hydrogen as defined above. Aprotic solventsinclude, for example, solvents such as hexanes, tetrahydrofuran (THF),acetonitrile, and benzonitrile. For a discussion of protic and aproticsolvents see Morrison and Boyd, Organic Chemistry, 5th Ed., pp. 228-231,(Allyn and Bacon, Inc. 1987).

The processes are preferably carried out in a protic reaction medium,that is, in a protic solvent alone or a mixture of solvents whichcontains at least one protic solvent. Preferred protic media include,but are not limited to water, aqueous media containing water and othersolvents, alcohols, and any media containing an alcohol, or mixtures ofsuch media.

The reaction between a diazonium salt and a carbon black can take placewith any type of carbon black, for example, in fluffy or pelleted form.In one embodiment designed to reduce production costs, the reactionoccurs during a process for forming carbon black pellets. For example, acarbon black product can be prepared in a dry drum by spraying asolution or slurry of a diazonium salt onto a carbon black.Alternatively, the carbon black product can be prepared by pelletizing acarbon black in the presence of a solvent system, such as water,containing the diazonium salt or the reagents to generate the diazoniumsalt in situ. Aqueous solvent systems are preferred.

In general, the processes produce inorganic by-products, such as salts.In some end uses, such as those discussed below, these by-products maybe undesirable. Several possible ways to produce a carbon black productwithout unwanted inorganic by-products or salts are as follows:

First, the diazonium salt can be purified before use by removing theunwanted inorganic by-product using means known in the art. Second, thediazonium salt can be generated with the use of an organic nitrite asthe diazotization agent yielding the corresponding alcohol rather thanan inorganic salt. Third, when the diazonium salt is generated from anamine having an acid group and aqueous NO₂, no inorganic salts areformed. Other ways may be known to those of skill in the art.

In addition to the inorganic by-products, a process may also produceorganic by-products. They can be removed, for example, by extractionwith organic solvents. Other ways of obtaining products without unwantedorganic by-products may be known to those of skill in the art, andinclude washing or removal of ions by reverse osmosis.

The reaction between a diazonium salt and a silica coated carbon blackforms a silica coated carbon black having an organic group attached tothe carbon black. The diazonium salt may contain the organic group to beattached to the silica coated carbon black. It may be possible toproduce the carbon black products by other means known to those skilledin the art.

The organic group may be an aliphatic group, a cyclic organic group, oran organic compound having an aliphatic portion and a cyclic portion. Asdiscussed above, the diazonium salt employed can be derived from aprimary amine having one of these groups and being capable of forming,even transiently, a diazonium salt. The organic group may be substitutedor unsubstituted, branched or unbranched. Aliphatic groups include, forexample, groups derived from alkanes, alkenes, alcohols, ethers,aldehydes, ketones, carboxylic acids, and carbohydrates. Cyclic organicgroups include, but are not limited to, alicyclic hydrocarbon groups(for example, cycloalkyls, cycloalkenyls), heterocyclic hydrocarbongroups (for example, pyrrolidinyl, pyrrolinyl, piperidinyl, morpholinyl,and the like), aryl groups (for example, phenyl, naphthyl, anthracenyl,and the like), and heteroaryl groups (imidazolyl, pyrazolyl, pyridinyl,thienyl, thiazolyl, furyl, indolyl, and the like). As the sterichinderance of a substituted organic group increases, the number oforganic groups attached to the carbon black from the reaction betweenthe diazonium salt and the carbon black may be diminished.

When the organic group is substituted, it may contain any functionalgroup compatible with the formation of a diazonium salt. Preferredfunctional groups include, but are not limited to, R, OR, COR, COOR,OCOR, carboxylate salts such as COOLi, COONa, COOK, COO⁻ NR₄ ⁺, halogen,CN, NR₂, SO₃ H, sulfonate salts such as SO₃ Li, SO₃ Na, SO₃ K, SO₃ ⁻ NR₄⁺, OSO₃ H, OSO₃ ⁻ salts, NR(COR), CONR₂, NO₂, PO₃ H₂, phosphonate saltssuch as PO₃ HNa and PO₃ Na₂, phosphate salts such as OPO₃ HNa and OPO₃Na₂, N═NR, NR₃ ⁺ X⁻, PR₃ ⁺ X⁻, S_(k) R, SSO₃ H, SSO₃ ⁻ salts, SO₂ NRR',SO₂ SR, SNRR', SNQ, SO₂ NQ, CO₂ NQ, S-(1,4-piperazinediyl)-SR,2-(1,3-dithianyl) 2-(1,3-dithiolanyl), SOR, and SO₂ R. R and R', whichcan be the same or different, are independently hydrogen, branched orunbranched C₁ -C₂₀ substituted or unsubstituted, saturated orunsaturated hydrocarbon, e.g., alkyl, alkenyl, alkynyl, substituted orunsubstituted aryl, substituted or unsubstituted heteroaryl, substitutedor unsubstituted alkylaryl, or substituted or unsubstituted arylalkyl.The integer k ranges from 1-8 and preferably from 2-4. The anion X⁻ is ahalide or an anion derived from a mineral or organic acid. Q is(CH₂)_(w), (CH₂)_(x) O(CH₂)_(z), (CH₂)_(x) NR(CH₂)_(z), or (CH₂)_(x)S(CH₂)_(z), where w is an integer from 2 to 6 and x and z are integersfrom 1 to 6.

A preferred organic group is an aromatic group of the formula A_(y)Ar--, which corresponds to a primary amine of the formula A_(y) ArNH₂.In this formula, the variables have the following meanings: Ar is anaromatic radical such as an aryl or heteroaryl group. Preferably, Ar isselected from the group consisting of phenyl, naphthyl, anthracenyl,phenanthrenyl, biphenyl, pyridinyl, benzothiadiazolyl, andbenzothiazolyl; A is a substituent on the aromatic radical independentlyselected from a preferred functional group described above or A is alinear, branched or cyclic hydrocarbon radical (preferably containing 1to 20 carbon atoms), unsubstituted or substituted with one or more ofthose functional groups; and y is an integer from 1 to the total numberof --CH radicals in the aromatic radical. For instance, y is an integerfrom 1 to 5 when Ar is phenyl, 1 to 7 when Ar is naphthyl, 1 to 9 whenAr is anthracenyl, phenanthrenyl, or biphenyl, or 1 to 4 when Ar ispyridinyl. In the above formula, specific examples of R and R' are NH₂--C₆ H₄ --, CH₂ CH₂ --C₆ H₄ --NH₂, CH₂ --C₆ H₄ --NH₂, and C₆ H₅.

Another preferred set of organic groups which may be attached to acarbon black are organic groups substituted with an ionic or anionizable group as a functional group. An ionizable group is one whichis capable of forming an ionic group in the medium of use. The ionicgroup may be an anionic group or a cationic group and the ionizablegroup may form an anion or a cation.

Ionizable functional groups forming anions include, for example, acidicgroups or salts of acidic groups. The organic groups, therefore, includegroups derived from organic acids. Preferably, when it contains anionizable group forming an anion, such an organic group has a) anaromatic group and b) at least one acidic group having a pKa of lessthan 11, or at least one salt of an acidic group having a pKa of lessthan 11, or a mixture of at least one acidic group having a pKa of lessthan 11 and at least one salt of an acidic group having a pKa of lessthan 11. The pKa of the acidic group refers to the pKa of the organicgroup as a whole, not just the acidic substituent. More preferably, thepKa is less than 10 and most preferably less than 9. Preferably, thearomatic group of the organic group is directly attached to the carbonblack. The aromatic group may be further substituted or unsubstituted,for example, with alkyl groups. More preferably, the organic group is aphenyl or a naphthyl group and the acidic group is a sulfonic acidgroup, a sulfinic acid group, a phosphonic acid group, or a carboxylicacid group. Examples of these acidic groups and their salts arediscussed above. Most preferably, the organic group is a substituted orunsubstituted sulfophenyl group or a salt thereof; a substituted orunsubstituted (polysulfo)phenyl group or a salt thereof; a substitutedor unsubstituted sulfonaphthyl group or a salt thereof; or a substitutedor unsubstituted (polysulfo)naphthyl group or a salt thereof. Apreferred substituted sulfophenyl group is hydroxysulfophenyl group or asalt thereof.

Specific organic groups having an ionizable functional group forming ananion (and their corresponding primary amines) are p-sulfophenyl(p-sulfanilic acid), 4-hydroxy-3-sulfophenyl(2-hydroxy-5-amino-benzenesulfonic acid), and 2-sulfoethyl(2-aminoethanesulfonic acid). Other organic groups having ionizablefunctional groups forming anions may also be used.

Amines represent examples of ionizable functional groups that formcationic groups. For example, amines may be protonated to form ammoniumgroups in acidic media. Preferably, an organic group having an aminesubstituent has a pKb of less than 5. Quaternary ammonium groups (--NR₃⁺) and quaternary phosphonium groups (--PR₃ ⁺) also represent examplesof cationic groups. Preferably, the organic group contains an aromaticgroup such as a phenyl or a naphthyl group and a quaternary ammonium ora quaternary phosphonium group. The aromatic group is preferablydirectly attached to the carbon black. Quaternized cyclic amines, andeven quaternized aromatic amines, can also be used as the organic group.Thus, N-substituted pyridinium compounds, such as N-methyl-pyridyl, canbe used in this regard. Examples of organic groups include, but are notlimited to, (C₅ H₄ N)C₂ H₅ ⁺, C₆ H₄ (NC₅ H₅)⁺, C₆ H₄ COCH₂ N(CH₃)₃ ⁺, C₆H₄ COCH₂ (NC₅ H₅)⁺, (C₅ H₄ N)CH₃ ⁺, and C₆ H₄ CH₂ N(CH₃)₃ ⁺.

An advantage of the carbon black products having an attached organicgroup substituted with an ionic or an ionizable group is that the carbonblack product may have increased water dispersibility relative to thecorresponding untreated carbon black. Water dispersibility of a carbonblack product increases with the number of organic groups attached tothe carbon black having an ionizable group or the number of ionizablegroups attached to a given organic group. Thus, increasing the number ofionizable groups associated with the carbon black product shouldincrease its water dispersibility and permits control of the waterdispersibility to a desired level. It can be noted that the waterdispersibility of a carbon black product containing an amine as theorganic group attached to the carbon black may be increased byacidifying the aqueous medium.

Because the water dispersibility of the carbon black products depends tosome extent on charge stabilization, it is preferable that the ionicstrength of the aqueous medium be less than 0.1 molar. More preferably,the ionic strength is less than 0.01 molar.

When such a water dispersible carbon black product is prepared, it ispreferred that the ionic or ionizable groups be ionized in the reactionmedium. The resulting product solution or slurry may be used as is ordiluted prior to use. Alternatively, the carbon black product may bedried by techniques used for conventional carbon blacks. Thesetechniques include, but are not limited to, drying in ovens and rotarykilns. Overdrying, however, may cause a loss in the degree of waterdispersibility.

In addition to their water dispersibility, carbon black having anorganic group substituted with an ionic or an ionizable group may bedispersible in polar organic solvents such as dimethylsulfoxide (DMSO),and formamide. In alcohols such as methanol or ethanol, use ofcomplexing agents such as crown ethers increases the dispersibility ofcarbon black products having an organic group containing a metal salt ofan acidic group.

Aromatic sulfides encompass another group of preferred organic groups.Carbon black products having aromatic sulfide groups are particularlyuseful in rubber compositions. These aromatic sulfides can berepresented by the formulas Ar(CH₂)_(q) S_(k) (CH₂)_(r) Ar' orA--(CH₂)_(q) S_(K) (CH₂)_(r) Ar" wherein Ar and Ar' are independentlysubstituted or unsubstituted arylene or heteroarylene groups, Ar" is anaryl or heteroaryl group, k is 1 to 8 and q and r are 0-4. Substitutedaryl groups would include substituted alkylaryl groups. Preferredarylene groups include phenylene groups, particularly p-phenylenegroups, or benzothiazolylene groups. Preferred aryl groups includephenyl, naphthyl and benzothiazolyl. The number of sulfurs present,defined by k preferably ranges from 2 to 4. Preferred carbon blacks arethose having an attached aromatic sulfide organic group of the formula--(C₆ H₄)--S_(k) --(C₆ H₄)--, where k is an integer from 1 to 8, andmore preferably where k ranges from 2 to 4. Particularly preferredaromatic sulfide groups are bis-para-(C₆ H₄)--S₂ --(C₆ H₄)-- andpara-(C₆ H₄)--S₂ --(C₆ H₅). The diazonium salts of these aromaticsulfide groups may be conveniently prepared from their correspondingprimary amines, H₂ N--Ar--S_(k) --Ar'--NH₂ or H₂ N--Ar--S_(k) --Ar".Preferred groups include dithiodi-4,1-phenylene,tetrathiodi-4,1-phenylene, phenyldithiophenylene,dithiodi-4,1-(3-chlorophenylene), --(4-C₆ H₄)--S--S--(2-C₇ H₄ NS),--(4-C₆ H₄)--S--S--(4-C₆ H₄)--OH, --6-(2-C₇ H₃ NS)--SH, --(4-C₆ H₄)--CH₂CH₂ --S--S--CH₂ CH₂ --(4-C₆ H₄)--, --(4-C₆ H₄)--CH₂ CH₂ --S--S--S--CH₂CH₂ --(4-C₆ H₄)--, --(2-C₆ H₄)--S--S--(2-C₆ H₄)--, --(3-C₆H₄)--S--S--(3-C₆ H₄)--, --6-(C₆ H₃ N₂ S), --6-(2-C₇ H₃ NS)--S--NRR'where RR' is --CH₂ CH₂ OCH₂ CH₂ --, --(4-C₆ H₄)--S--S--S--S--(4-C₆H₄)--, --(4-C₆ H₄)--CH═CH₂, --(4-C₆ H₄)--S--SO₃ H, --(4-C₆ H₄)--SO₂NH--(4-C₆ H₄)--S--S--(4-C₆ H₄)--NHSO₂ --(4-C₆ H₄)--, --6-(2-C₇ H₃NS)--S--S-2-(6-C₇ H₃ NS)--, --(4-C₆ H₄)--S--CH₂ --(4-C₆ H₄)--, --(4-C₆H₄)--SO₂ --S--(4-C₆ H₄)--, --(4-C₆ H₄)--CH₂ --S--CH₂ --(4-C₆ H₄)--,--(3-C₆ H₄)--CH₂ --S--CH₂ --(3-C₆ H₄)--, --(4-C₆ H₄)--CH₂ --S--S--CH₂--(4-C₆ H₄)--, --(3-C₆ H₄)--CH₂ --S--S--CH₂ --(3-C₆ H₄)--, --(4-C₆H₄)--S--NRR' where RR' is --CH₂ CH₂ OCH₂ CH₂ --, --(4-C₆ H₄)--SO₂NH--CH₂ CH₂ --S--S--CH₂ CH₂ --NHSO₂ --(4-C₆ H₄)--, --(4-C₆H₄)-2-(1,3-dithianyl), and --(4-C₆H₄)--S--(1,4-piperizinediyl)--S--(4-C₆ H₄)--.

Another preferred set of organic groups which may be attached to thecarbon black are organic groups having an aminophenyl, such as (C₆H₄)--NH₂, (C₆ H₄)--CH₂ --(C₆ H₄)--NH₂, (C₆ H₄)--SO₂ --(C₆ H₄)--NH₂.Preferred organic groups also include aromatic sulfides, represented bythe formulas Ar--S_(n) --Ar' or Ar--S_(n) --Ar", wherein Ar and Ar' areindependently arylene groups, Ar" is an aryl, and n is 1 to 8. Methodsfor attaching such organic groups to carbon black are discussed in U.S.patent applications Ser. Nos. 08/356,660, 08/572,525, and 08/356,459,the disclosures of which are fully incorporated by reference herein.

In addition, a mixture of silica coated carbon black and a modifiedcarbon black having at least one attached organic group may be used.Furthermore, it is within the bounds of this application to also use amixture of silica and silica coated carbon black. Also, any combinationof additional components with the silica coated carbon black may beused, such as one of the following:

a) silica coated carbon black with an attached organic group optionallytreated with silane coupling agents;

b) modified carbon black having an attached organic group;

c) silica;

d) modified silica, for example, having an attached organic group;and/or

e) carbon black.

Examples of silica include, but are not limited to, silica, precipitatedsilica, amorphous silica, vitreous silica, fumed silica, fused silica,silicates (e.g., aluminosilicates), and other Si-containing fillers suchas clay, talc, wollastonite, and the like. Silicas are commerciallyavailable from such sources as Cabot Corporation under the Cab-O-Sil®tradename, PPG industries under the Hi--Sil and Ceptane tradenames,Rhone-Poulence under the Zeosil tradename; and Degussa AG under theUltrasil and Coupsil tradenames.

Any suitable elastomer may be compounded with the silica coated carbonblacks to provide the elastomeric compounds of the present invention.Such elastomers include, but are not limited to, homo- or co-polymers of1,3 butadiene, styrene, isoprene, isobutylene,2,3-dimethyl-1,3-butadiene, acrylonitrile, ethylene, and propylene,preferably wherein the glass transition temperature (Tg) as measured byDifferential Scanning Calorimetry (DSC) ranges from about -120° C. toabout 0° C. Examples include, but are not limited to, SBR, naturalrubber and its derivatives such as chlorinated rubber, polybutadiene,polyisoprene, poly(styrene-co-butadiene), and blends of any of theforegoing. SBRs include, but are not limited to, solution SBR,functional solution SBR, emulsion SBR, and combinations of any of theforegoing.

The silica coated carbon black of the invention may also be used withsynthetic rubbers such as: copolymers of from about 10 to about 70percent by weight of styrene and from about 90 to about 30 percent byweight of butadiene such as copolymer of 19 parts styrene and 81 partsbutadiene, a copolymer of 30 parts styrene and 70 parts butadiene, acopolymer of 43 parts styrene and 57 parts butadiene and a copolymer of50 parts styrene and 50 parts butadiene; polymers and copolymers ofconjugated dienes such as polybutadiene, polyisoprene, polychloroprene,and the like, and copolymers of such conjugated dienes with an ethylenicgroup-containing monomer copolymerizable therewith such as styrene,methyl styrene, chlorostyrene, acrylonitrile, 2-vinyl-pyridine, 5-methyl2-vinylpyridine, 5-ethyl-2-vinylpyridine, 2-methyl-5-vinylpyridine,alkyl-substituted acrylates, vinyl ketone, methyl isopropenyl ketone,methyl vinyl either, alphamethylene carboxylic acids and the esters andamides thereof such as acrylic acid and dialkylacrylic acid amide; alsosuitable for use herein are copolymers of ethylene and other high alphaolefins such as propylene, butene-1 and pentene-1.

Elastomeric compositions also include vulcanized compositions (VR),thermoplastic vulcanizates (TPV), thermoplastic elastomers (TPE), andthermoplastic polyolefins (TPO). TPV, TPE, and TPO materials are furtherclassified by their ability to be extruded and molded several timeswithout loss of performance characteristics.

In making the elastomeric compositions, one or more curing agents suchas, for example, sulfur, sulfur donors, activators, accelerators,peroxides, and other systems used to effect vulcanization of theelastomer composition may be used.

The elastomeric compositions of the present invention may contain anelastomer, curing agents, reinforcing filler, a coupling agent, and,optionally, various processing aids, oil extenders, and antidegradents.

Formulation of the silica coated carbon blacks of the present inventionwith elastomers are contemplated to have advantages not realized whensuch elastomers are formulated with conventional carbon blacks. Setforth below in Table 1 is a list of certain of the elastomers which areparticularly useful for industrial rubber applications; and preferredloading ratios with the silica coated carbon blacks of the presentinvention, designated as parts of carbon black per hundred parts ofelastomer (PHR); contemplated benefits obtained by such compositioncompared to the same composition employing a conventional carbon black;and useful industrial applications for each composition corresponding,where applicable, to the contemplated benefit obtained with suchcomposition. In addition to EPDM and peroxide cured elastomers,advantages for this silica coated carbon black would also be expected inelastomers containing elements other than carbon and hydrogen. Examplesof elastomers containing non-hydrogen groups would include but not belimited to NBR (acrylonitrile-butadiene rubber), XNBR(carboxylic-acrylonitrile-butadiene rubber), HNBR(hydrogenated-acrylonitrile-butadiene rubber), CR (chloroprene rubber),ECO (ethylene oxide-chloromethyl oxirane), GPO (polypropyleneoxide-allyl glycidyl ether), PPO (polypropylene oxide), CSM(chloro-sulfonyl-polyethylene), CM (chloro-polyethylene), BIIR(bromo-isobutene-isoprene rubber), CIIR (chloroisobutene-isoprenerubber), ACM (copolymers of ethyl or other acrylate and small amount ofvulcanizable co-monomer), and AEM (copolymers of ethyl or other acrylateand ethylene).

The contemplated benefits obtained with the compositions set forth inTable 1 are characterized by expected properties compared to the samecomposition made with conventional (non-silica coated) carbon black.Evaluation of these properties for a given silica coated carbonblack/elastomer composition is done by conducting comparative tests.Most of the properties set forth in Table 1 are determined by routinetests known to those skilled in the art. Other tests are brieflydescribed below:

Hardness refers to Shore A Hardness, which is determined according tothe procedure set forth in ASTM D-2240-86.

Resilience may be determined according to the procedure set forth inASTM D1054, utilizing a ZWICK Rebound Resilience Tester, Model 5109,manufactured by Zwick of America, Inc., Post Office Box 997, EastWindsor, Conn. 06088.

                                      TABLE 1    __________________________________________________________________________                                       FIELD OF    POLYMER  LOADING                    BENEFITS UPON FORMING                                       APPLICATION    __________________________________________________________________________    Ethylene  50-250 PHR                    INCREASED UHF HEATING RATES                                       WEATHERSTRIP    Propylene Diene             100-200 PHR                    INCREASED TEAR STRENGTH                                       WEATHERSTRIP    Monomer (EPDM)  REDUCED IRIDESCENCE                                       WEATHERSTRIP                    IMPROVED HEAT AGING RESISTANCE                                       HOSE                    HIGHER ELECTRICAL RESISTIVITY                                       HOSE                    INCREASED ELONGATION @ GIVEN                                       HOSE                    HARDNESS                    LONGER FATIGUE LIFE                                       ENGINE MOUNTS                    LOWER SPRING RATIO FOR A GIVEN                                       ENGINE MOUNTS                    TAN δ                    IMPROVED RESILENCE ENGINE MOUNTS    Poly-Chloroprene              10-150 phr                    LOWER SPRING RATIO FOR A GIVEN                                       ENGINE MOUNTS    (NEOPRENE)             20-80 phr                    TAN δ                    IMPROVED GLYCOL RESISTANCE                                       SEALS                    IMPROVED RESILENCE SEALS, HOSE                    LOWER HEAT BUILD-UP                                       BELTS    Natural Rubber              10-150 phr                    LOWER SPRING RATIO FOR A GIVEN                                       ENGINE MOUNTS    (NR)     20-80 phr                    TAN δ                    HIGHER CUT/CHIP RESISTANCE                                       BELTS    Hydrogenated              10-150 phr                    LOWER SPRING RATIO FOR A GIVEN                                       ENGINE MOUNTS    Nitrile Butadiene             20-80 phr                    TAN δ    Rubber          INCREASED HIGH TEMP TEAR                                       MOUNTS, SEALS    (HNBR)          RESISTANCE                    IMPROVED RESILIENCE                                       SEALS, HOSE                    LOWER HEAT BUILD-UP                                       BELTS    Styrene Butadiene              10-150 phr                    HIGHER CUT/CHIP RESISTANCE                                       BELTS    Rubber    (SBR)    Ethylene Vinyl              10-150 phr                    IMPROVED PHYSICAL PROPERTIES                                       HOSE    Acetate    (EVA)    __________________________________________________________________________

The UHF microwave receptivity may be measured by a Dielecmeter (suppliedby Total Elastomers in France). The UHF microwave receptivity ischaracterized by a coefficient, α, which is defined as

    α=(150° C.-80° C.)/(t.sub.150 -t.sub.80)  ° C./s!

where t₁₅₀ and t₈₀ are the times needed for samples to reach 150° C. and80° C. respectively. α is the heating rate between temperatures 80° and150° C.

The electrical resistivity of the composition may be measured bypainting samples 2 inches wide by 6 inches long by 0.085 inch thick witha half inch width of silver paint. The sample is then conditioned toproduce a stable reading by cycling from room temperature to 100° C. andback to room temperature, followed by aging at 90° C. for 24 hours. Thestabilized resistivity was measured at the end of the aging cycle, andonce again after the sample was allowed to cool back to roomtemperature.

The resultant elastomeric compounds containing silica coated carbonblack and optionally containing one or more coupling agents may be usedfor various elastomeric products such as treads for vehicle tires,industrial rubber products, seals, timing belts, power transmissionbelting, and other rubber goods. When utilized in tires, the elastomericcompounds may be used in the tread or in other components of the tire,for example, the carcass and sidewall.

Tread compounds produced with the present elastomeric compoundsincorporating a silica coated carbon black but without a coupling agent,provide improved dynamic hysteresis characteristics. However,elastomeric compounds incorporating a partially coated carbon black anda coupling agent demonstrate further improved characteristics.

All patents, applications, test methods, and publications mentionedherein are incorporated by reference.

Many variations of the present invention will suggest themselves tothose skilled in the art in light of the above detailed disclosure. Forexample, the compositions of the present invention may include otherreinforcing agents, other fillers, oil extenders, antidegradants, andthe like. All such modifications are within the full intended scope ofthe claims.

We claim:
 1. An elastomeric compound comprising:an elastomer selectedfrom the group consisting of ethylene propylene diene monomer rubber,poly chloroprene, natural rubber, hydrogenated nitrile butadiene rubber,nitrile butadiene rubber, chlorinated polyethylene, styrene butadienerubber, butyl rubber, polyacrylic rubber, polyepichlorohydrin, ethylenevinyl acetate and blends of the foregoing; and a silica coated carbonblack, and wherein at least a portion of said silica coated carbon blackhas an organic group attached thereto, and is optionally treated with asilane coupling agent.
 2. The elastomeric compound of claim 1 whereinsaid silica coated carbon black is present in an amount of from betweenabout 10 and 300 parts per hundred parts of said elastomer.
 3. Theelastomeric compound of claim 2 wherein said silica coated carbon blackis present in an amount of from between about 100 and 200 parts perhundred parts of said elastomer.
 4. The elastomeric compound of claim 1wherein said silica coated carbon black is present in an amount of frombetween about 10 and 150 parts per hundred parts of said elastomer. 5.The elastomeric compound of claim 4 wherein said silica coated carbonblack is present in an amount of from between about 20 and 80 parts perhundred parts of said elastomer.
 6. An article of manufacture formedfrom the elastomeric compound of claim
 1. 7. The article of claim 6wherein said elastomeric compound is formed into weatherstripping. 8.The article of claim 6 wherein said elastomeric compound is formed intocoolant hose.
 9. The article of claim 6 wherein said elastomericcompound is formed into hydraulic hose.
 10. The article of claim 6wherein said elastomeric compound is formed into fuel hose.
 11. Thearticle of claim 6 wherein said elastomeric compound is formed into anengine mount.
 12. The article of claim 6 wherein said elastomericcompound is formed into a bushing.
 13. The article of claim 6 whereinsaid elastomeric compound is formed into a power belt.
 14. The articleof claim 6 wherein said elastomeric compound is formed into a conveyorbelt.
 15. The article of claim 6 wherein said elastomeric compound isformed into a power transmission belt.
 16. The article of claim 6wherein said elastomeric compound is formed into a seal.
 17. The articleof claim 6 wherein said elastomeric compound is formed into a gasket.18. An elastomeric compound comprising an elastomer and a silica coatedcarbon black, wherein said carbon black is at least partially coatedwith silica, andwherein at least a portion of said silica coated carbonblack has an organic group attached thereto, and is optionally treatedwith a silane coupling agent.
 19. The elastomeric compound of claim 18,wherein said elastomer is selected from the group consisting of solutionSBR, natural rubber, functional solution SBR, emulsion SBR,polybutadiene, polyisoprene, and blends of any of the foregoing.
 20. Theelastomeric compound of claim 18, wherein said silica coated carbonblack contains between about 0.5% and about 10% silicon, by weight. 21.The elastomeric compound of claim 20, wherein said silica coated carbonblack contains between about 2% and about 6% silicon, by weight.
 22. Theelastomeric compound of claim 18 further comprising a coupling agent.23. The elastomeric compound of claim 22, wherein said coupling agent isselected from the group consisting of silane coupling agents, zirconatecoupling agents, titanate coupling agents, nitro coupling agents, andmixtures of any of the foregoing.
 24. The elastomeric compound of claim23, wherein said coupling agent is selected from the group consisting ofbis(3-triethoxysilylpropyl)tetrasulfane, 3-thiocyanatopropyl-triethoxysilane, γ-mercaptopropyl-trimethoxy silane, zirconiumdineoalkanolatodi(3-mercapto) propionato-O,N,N'-bis(2-methyl-2-nitropropyl)-1,6-diaminohexane and mixtures of theforegoing.
 25. A method for improving the hysteresis of an elastomericcompound comprising compounding an elastomeric compound as defined inclaim 18, wherein said silica coated carbon black imparts to theelastomer higher loss tangent at low temperature and a lower losstangent at high temperature, compared to an uncoated carbon black. 26.The elastomeric compound of claim 1, further comprising silica.
 27. Theelastomeric compound of claim 1, further comprising carbon black,silica, or combinations thereof.
 28. The elastomeric compound of claim18, wherein said organic group is Ar--S_(n) --Ar' or Ar--S_(n) --Ar",wherein Ar and Ar' are independently arylene groups, Ar" is an aryl, andn is 1 to
 8. 29. The elastomeric compound of claim 1, further comprisinga carbon black having an organic group attached thereto.
 30. Theelastomeric compound of claim 1, further comprising carbon black. 31.The elastomeric compound of claim 1, wherein said elastomericcomposition further comprises a carbon black having an organic groupattached thereto, silica, carbon black, or mixtures thereof.
 32. Aformulation for making an elastomeric composition, comprising anelastomer and a silica coated carbon black, wherein at least a portionof said silica coated carbon black has an organic group attachedthereto, and is optionally treated with a silane coupling agent.
 33. Theformulation of claim 32, further comprising a coupling agent.